The monster underneath the surface
by evelina.nyman.7
Summary: After a fight, Donnie starts to act different and behave different. And as the time goes by even his body goes through changes. And while that happens, a man called Dirk Savage has started to hunt down mutants in the city and the rest of the team must find a way to stop him and save and cure their brother. Based on the Good Genes episodes.
1. Chapter 1, Who is this Dirk Savage?

The monster underneath the surface

**A/N: Hooray, I'm back! And I plan this earlier, but I have been tired and the heat here has been pitiless and dried away my energy, but I wrote as fast and as long as I could. By the way I want to give you all a great big thank you for giving me 98 REVIEWS on my last story! Thank you so much! I had hoped for 100 reviews but I'm not going to be ungrateful.**

**And I just want to make one thing clear, I did make a version of this when I started to write on , but back then I was terrible at English grammar and the only reason I keep it up is because I like to see how much better I am now than back then, so you don't have to read it. Actually, please ignore it. **

**A little info about the story. Again, there are no ice powers! And I am borrowing two character's name from the 1980's and 2k3 cartoons, and they will be "the bad guys" with a little Kraang, just so you know. And Karai hasn't switched sides, yet. And this story might be shorter than my other story, but I don't promise anything now. Anyway, on with the story! And excuse my Kraang language. Enjoy and please review!**

Chapter 1, Who's this Dirk Savage?

* * *

(Normal P.O.V)

Inside TCRI the Kraang was standing by a large machine with a giant container with a more purple mutagen, than the usual blue-green kind. One Kraang-bot walked up to two others, who was working on the machine.

"Kraang, is that which is known as experiment 37 that which is known as perfected?" One robots was pushing on some buttons and typing on a computer, but the other turned to answer the other Kraang's question.

"Negative Kraang. That which as known as experiment 37 has shown to be that which is known as difficult to perfect. The molecules has proved to be what is known as-" The Kraang was interrupted as he was hit with a bullet right in the head. The robot body fell to the ground, and the small, squishy pink alien jumped out and ran across the floor while squealing. The other Kraang-bots in the lab looked up from the big machine, some picked up their weapons and tried to find the one who had fired the gun. The one that seemed to be the leader had one of the Kraang guns in his hands and called out into the room.

"Kraang demands that the one who is in this place who is not allowed to be in this place will come out and let Kraang escort you to a place where-" Another shot was heard and the robot fell to the ground and another little alien escaped from the robot and ran out of the room. A muscular woman escaped from the shadows and punched one of the robots in the head and threw another one into the wall. And a tall dark man walked up with a gun in his hand.

"If you value your lives Kraang, leave this room. Now!" The Kraang refused to leave the room and one of them pointed to the man with his gun.

"The order given from the one who is in this place that is not allowed to be in this can not be followed by Kraang. Kraang must force you to come with us to-" But the man had other ideas. He fired a shot at the Kraang's body and the bullet was close to hit the pink flesh.

"Leave, now!" The remaining Kraang left the room, but the man still shot their robot bodies, making the small aliens escape. The woman walked up to the computer and started to type at it. The man walked up to her and had his arms crossed over his chest.

He had dark hair and was very muscular and had a belt with guns around his waist, all with different kinds of bullets with different effects, like tranquilizing, throwing nets or simply to kill someone. He was dressed in cargo pants with camouflage patterns and a black sleeveless shirt and two belts with bullets in a cross over his chest. His feet was covered in black leather boots that went up to his lower calves His face was serious, his chin was covered in stubble and over his face ran a long scar the started on his forehead, just over his left eyebrow and stretched down, over the bridge of his nose and ended right at the corner of his mouth.

"Have you found what we are looking for, Abigail?" The woman, Abigail, looked up from the computer and met the man's eyes. She had brown hair, pulled into a ponytail, had green eyes and was dressed in a tight, black shirt and the sleeves went down to her elbows and she had cargo pants too, but they were beige and not camouflage colored. And she walked around in sneakers and on her hands was fingerless gloves and she had a tattoo of a black dragon on her left shoulder.

"Yes, I've found the plans for experiment 37 and the substance in the tubes should be the substance we are looking for. But the notes say it's not perfect yet, but I think it will work in our plan anyway." The man nodded and smirked evilly.

"Excellent. Gather us much info about their new mutagen as you can. I will get the truck and start loading it with as much mutagen as the truck can fit. Soon our plan can finally get started."

* * *

(Donnie's P.O.V)

The day had been relatively calm. Raph and Leo had not been fighting _too_ much and Mikey had been glued to the TV and had looked through the channels and the video tapes for something to watch. And I had tried to look through some Kraang files we had found the other night on patrol in TCRI. Well I had found a storage device in one of their labs and was trying to find something about their invasion plans or something useful to know.

We were all sitting in the living room doing our own stuff. Raph was reading one of his issues of 'Modern Ninja Magazine' and tried to look as if he wasn't annoyed by Mikey switching channels all the time so he heard the same stuff over and over. Leo was training with the training dummy in the living room and tried to block everything out too. And I was looking through the files and tried so hard to find anything good that we didn't already know or wasn't damaged.

"Mikey! Can't you just pick something to watch? It's starting to get on my nerves to hear everything over and over! If you can't watch anything just turn off the TV!" Mikey turned to Raph and he also looked annoyed.

"Do you mind? I'm trying to watch TV here! Can you tone down the yelling?" Raph was silent for one second, then he flew up from the couch, dropped the magazine on the floor and pried the remote from Mikey's fingers and tried to turn the TV off, but Mikey grabbed the remote and tried to get it back.

"Hey, give it back!" Raph held the remote away from him and they started to fight over the remote. Leo had turned around to look at our brothers on the floor fighting, yelling and wrestling over the remote. He and I shared a look and I saw in his eyes that we shouldn't get involved. They would end soon anyway. Raph would press Mikey too the ground and pry the remote from his hand and turn it off. I looked down at my laptop again and saw something interesting and skimmed through it. Then I looked up at my brothers.

"Hey guys, I think I found something about the Kraang!" Raph and Mikey looked up from their wrestling match and Leo stopped punching his dummy and they all gathered around me and Leo looked at the screen, trying to see what it was.

"I found something that says the Kraang are trying to create some new kind of mutagen. Something they call experiment 37." Raph looked a little confused and tried to see anything he could understand on the screen.

"New mutagen? Why would they want a new kind of mutagen? I thought the one they had was unpredictable and they needed April to make it right." I looked down and read through it again and then gave my answer.

"Yeah, but this one is supposed to mutate your brain, and not your body. To either make you like a robot and would obey your every order, in case they have abilities the Kraang find useful. Or they could mutate you mind, making you more or less like an animal. I guess it's for making humans attack and kill each other so the Kraang can focus on other things. But it's all I can find now." Leo read through the text a little and then looked at me.

"So they plan to use it on humans?" I shook my head and looked back to the computer.

"No, it says here they haven't quite got it right yet. The molecular structure won't mutate the way it's supposed to and that makes the mutagen mutate the body and still makes you act like an animal, or a predator." Mikey looked over my shoulder and his cheek was pressed into my face.

"But why is it such a big deal if they can't use it yet? It's not like they're going to use something that doesn't work, right?" I pushed him away from my face, making him fall to the floor and groaned from the fall.

"Maybe if you guys would let me finish I could tell you." I turned back to the computer.

"It says here that last week a big amount of the defect mutagen was stolen, by _humans_." I saw the confusion on their faces and Mikey flew up from the floor and sat on his knees and rubbed his head, before the TV distracted him. Raph looked at with a raised eyebrow.

"How can humans know about the Kraang? I mean, I know they invaded Earth last year but that doesn't make the humans know what the Kraang are or what they want or do?" I was about to answer but Mikey was faster.

"Guys, listen to this!" We looked at the TV and saw Mikey and Raph had left channel 6 news on and we saw that Carlos Gamble interview a dark man that looked like he walked right out of a action movie. And beside him stood a woman who also looked really tough.

"_I stand here with mutant hunter Dirk Savage and his assistant doctor Abigail Finn and we talk about his promise to clean the streets of mutants here in our fair city._" I felt my ninja sense tingle and looked at Leo, who also looked cautious and alert.

"Mutant hunter? That doesn't sound good." Raph shushed him and was staring at the TV screen. The man, who I assumed was Dirk Savage was talking and he even sounded intimidating.

"_Well Carlos, my job is to wipe out scum from this world. Unwelcome guests that think they can walk on our streets like normal people. I and my brave assistant Abigail work to destroy hunt down these threats and destroy them._" Carlos looked a little scared but asked a new question.

"A_nd h-how do you know that there are mutants in this city? Or in our world for that matter?_" Dirk smirked evilly and I felt a chill run down my spine.

"_Because I have prof right here._" He nodded at Abigail and she walked up a giant covered cylinder shaped item and pulled of the cover and it revealed a big container, a big technological cage and in it was a big mutant bear with big teeth, long claws and big muscles in the legs and arms. We gasped at the sight and Carlos hid behind Dirk Savage with a small, girly shriek.

"_What you see here is an example of what nature can create with a small ounce of what is called mutagen._" I felt my heart stop beating when he held up a canister with mutagen, but got suspicious when I realized that the "mutagen" was purple and not blue-green like it usually was.

"_One little drop of this substance, and any creature can turn into a monstrosity, a freak of nature or simply a mutant. Where this hideous substance comes from is not relevant, but I can tell you that I am here to wipe these mutants off the streets, every single one will the wiped off the face of Earth! And nothing will stop us!_" Wow, for someone who claimed he was on the people's side he sounded too intimidating. Mikey shuddered and I heard a small whimper from him. Raph looked angry, but I saw a very small trace of fear in his eyes too. Leo was listening closely to what was said on the TV and he looked both concerned and suspicions.

"_And, h-how do you plan on finding these m-mutants? I mean, what advantages do you have against them?_" Dirk smirked and put his hand on Abigail's shoulder and she smiled with pride and a little malice.

"_Abigail here has created tracking systems and weapons against these freaks. Tranquilizers strong enough to knock out a blue whale and firepower strong enough to kill them if necessary or just simple but strong nets and containment units strong enough to hold them. And we have electrical weapons that can break them if necessary. And both she and me has experience of fighting in battle. So I do think we are ready for fighting these mutants. And if anyone see's a mutant, you can call us and tell us where you've seen it and what kind of mutant._" Raph turned off the TV and turned to Leo.

"Okay, that was a little weird. How did those two know about mutagen? Or mutants for that matter?" Leo rested his chin in his hand and hummed in thought.

"Yeah, and who is this Dirk Savage anyway? I mean, where did he come from and what kind of person is he? A warrior, a scientist or what?" I looked down at my computer and brought internet up and started to type on the keyboard.

"I'm on it!" I looked through a few files, websites and news pages before I found what I was looking for.

"Here! It says here that Dirk Savage is a sort of bounty hunter and soldier and has hunted and taken down what people has considered threats for governments all over the world. That being gypsies, jews, predators, rebels, misfits and other outcasts. And this Abigail Finn, his assistant is a scientist in gifted in both biology and technology and was working for TCRI until last year and started to work with Dirk. That's all I can find on who they are." Leo looked over my shoulder and read through the text too and sighed a little.

"Well, at least we know who they are." Raph stood up and walked over to us with a frown on his face.

"Yeah, but that doesn't answer the question how he knows about mutagen or the mutants in this city! I mean, not that many people have seen mutants and gotten evidence of them! And don't get me started on the mutagen!" I rubbed my chin and thought about the purple color the mutagen had.

"What if it isn't mutagen? Or at least the mutagen we know about. I mean, the mutagen was purple and not green. And if it is mutagen, does that mean they know of the Kraang?" Leo opened his mouth, but Mikey was faster.

"Maybe that girl who worked for TCRI learned about the Kraang and later told Dirk Savage about it and the mutagen. And they broke into TCRI or one of their labs and stole that purple goo?" Raph, Leo and I just stared at him and then looked at each other and back to Mikey.

"That, is a a brilliant theory Mikey." Mikey looked surprised too and dropped his little smile.

"It is? Uh- I mean, of course it is bro. You really should listen to me more often." Leo rolled his eyes and looked back at the laptop and looked through the text again.

"Does this guy have a lair or some kind of hideout or something?" I looked through the search options but didn't find what I was looking for. But I found something else.

"No, but I found their number you call when you find a mutant. I can track the phone with that number and find Savage anyway." Leo stood up and picked up katana's from the floor.

"Well then. We'll go out there and look for these guys and find out more about what they do with the mutagen and with the mutants. It could be good to know how good they are if we run into them when we're out in the city." I started to type again and started to track the phone and soon I found the coordinates.

"And his coordinates are at..." When I saw the location on the screen I got a little surprised. "at an old abandoned warehouse at Houston street?" The other looked surprised too and Raph looked at the map too.

"A warehouse? Why would he hide at a warehouse?" I shrugged and closed the laptop and stood up.

"I guess we're going to find out. Let's go and find out the answers." And we ran towards the exit of the lair and towards the nearest manhole.

If I had known what would happen this week I would have said we should stay in the lair for now, but for now I ran out into the unknown without knowing that this night would have more effect on me than my brothers and that the event would haunt me and them for the rest of our lives.

* * *

**A/N: First chapter's done and I feel the villains and the plot with them is a little lazy, but story is now going to be so much about them so I hope you won't mind anyway. And please, tell me how I can do this better if it's not as good as it can be. If I can do anything better, please tell me. And please favorite, follow and review. **


	2. Chapter 2, A tiny error and new behavior

The monster underneath the surface

**A/N: Okay, a new update! Yay. Sorry for being a little late, but I wanted to fit a lot into this and we have been painting in my room so I had to unplug the computer for a few days. **

**And I also wanted to say that in less than two weeks I'm going to high school and I may not be able to update as fast as I usually can. Just a warning. **

**And thanks to everyone who has reviewed so far and please, give me your thoughts on how I can do better, or just to tell how you like it.**

Chapter 2, A tiny error and new behavior

* * *

(Leo's P.O.V)

The night was silent. Not much, other than a few cars, one or two alley cats or talking from the humans on the street, was heard. But we made sure no one saw us anyway. We jumped from roof to roof in complete silence. Or I wished it had been in complete silence anyway.

"Booyakasha!" Mikey's voice was heard as he jumped from roof to roof and in every other jump he did a flip or a "cool move" as he put it and also cried out his little catchphrase a little too often. Raph growled and ran up to him and grabbed his mask tails and yanked on them, hard. Mikey stopped running and cried out in surprise and a little pain.

"Mikey, in case you didn't know, we are ninjas! And ninjas use stealth and silence! So can you please try to be more quiet?" I didn't want to sound harsh, but I didn't want Mikey to give us away or people to see us and call that Dirk Savage either. Mikey just shrugged and pretended to close a zipper over his lips.

"Shh, quiet guys! There are humans on the street under us and they're looking up here!" Donnie pointed to the pavement and Raph and I looked down too and saw a girl with short black hair and a blue skirt and she was talking to April. I was about to tell my brothers to keep moving when I heard that other girl talking about something that made me interested.

"So have you heard about that Dirk Savage guy before? I heard that he has taken down a giant army of beefy soldiers all on his own! And that he is missing a part of his ear and his left foot!" So the word was already out. April just shrugged at her friends words.

"I haven't heard that much about him Irma. I didn't even know his name or who he was until I saw the newscast. But I've never heard about him before, and I didn't know there was mutants in this city." The girl, who appeared to be named Irma, just shrugged too.

"Me neither. I say the guy is a fake that just wants attention. It'll blow over in a few days, maybe a week." I made a signal to my brothers and we started to run down the street and to Houston Street. And it didn't take long before we got there. I looked just like any other warehouse and outside the building there was a big black van.

"Looks like we're here. Now what's the plan, fearless leader?" Raph asked and glanced at me with a small frown on his face. I thought it over and looked at a small window on the side and then thought up a plan.

"Okay, we go through that window and then find this Dirk Savage person and find out more about him. No fighting and no sabotaging unless there is a reason to, got it?" Mikey and Donnie nodded, but Raph didn't look too happy about the idea but he mumbled 'you're the boss' under his breath and Donnie placed his staff about a foot over the ground so we place one foot on it and then jump up to the window. He then used the staff to heave himself up and we all crawled in through the window.

We saw a corridor that lead to a big door that was slightly open and the light of a bright lamp was shining through the little opening. Over the door was a ventilation shaft, big enough for us to go through. I made a small gesture at the shaft and we made our way through the corridor. Raph cupped his hands for us to step on and one after one of us jumped up the ventilation shaft and we crawled through and he jumped after us and we helped him up, although he didn't acknowledge it. We didn't have to crawl long before we saw a new opening and crowded around it to see through. But what I saw was enough to make me wish I hadn't seen any of it.

There was Dirk and his assistant Abigail was standing at a big container made of glass, similar to the one we saw on the news with that mutant bear in, and Abigail was working at some computer on the container. Savage was standing beside her with his arms crossed and he looked impatient. And in a corner of the room was a big vat with purple, glowing mutagen.

"Is the preparations finished yet Abigail? We don't have all night you know!" Abigail looked away from the computer and she pressed her face up against him, standing on her toes seeing how she was shorter than him. But I wasn't fooled, I could see she was both strong and tough as iron.

"It might go a little faster if you decided to help out Dirk! But all you've got is muscles and a hot temper, right? And I've got both brains and brawn but I have to do all the work, right?" He didn't seem the least bit fazed by her words and just glared at her with no emotion or frown on his face.

"Do I need to remind you what we are doing here Abigail? This city is crawling with mutants, freaks and aliens and if we want people to take us seriously we have to show that there are real mutants here. First then, when people see what we do and start to trust us, can we show the aliens too and get people to pay attention to them and once they are gone, our world can finally be free from freaks. You haven't forgotten about that, have you?" Abigail didn't say anything, she just turned back to her computer. But I started to understand what their plan was. They weren't just after the mutants, but the Kraang too.

"Did you hear that? They're after the Kraang too! Is that considered good or bad?" Donnie whispered and I shrugged slightly. I didn't know what to think about it.

"But if they want to fight the Kraang, then why do they have all that weird mutagen? Is that a way of stopping their plans or something?" Raph whispered back. I saw Dirk drag a human across the room and hushed at the others.

"Shh, here he comes again and I want to see and hear what happens." The poor man was tied around his hands and had a panic attack and tried to protest. I recognized him, it was the guy we saved from the Kraang's brain-switching plan. Looks like this guy couldn't get a break. Abigail turned away from the computers again and pressed a button on the containment unit and a door opened in the side.

"The preparations are finished and we're good to go. But I don't see why we're using stuff that those freaky brain-blobs have created. Aren't they the enemy?" Dirk smirked a little and tightened his grip on the man, who almost had stopped breathing and looked very pale.

"Sometimes you have to use other methods to do what's right. Even if that means doing something that's not ethically right. Prepare the DNA and the mutagen!" The man started to fight back and tried to run away, but was pushed into the container and the door closed behind him and locked itself. Raph had his hands on his sai, ready to defend the poor man and I put my hands on the hilt of my katana and signaled to the others to get ready. Donnie used his staff to open the hatch and we jumped down to the floor. But we were a bit too late, the mutagen had already been put in a needle and was placed at the mans neck through a hatch onthe side of unit and the fluid was flowing into the man's neck. We jumped in behind a few craters and watched the scene in horror.

The man was growing both in length and muscles mass. His skin was turning green/brown and his nose and mouth stretched and got longer and his teeth got longer, sharper and there was more than just 32 teeth (which is the average amount) and his legs and arms got shorter, but stronger and his fingers and toes got claws. His cloths ripped and his voice turned from painful screams to a painful roar. And his eyes looked like Leatherhead's eyes. The poor man had turned into a mutant crocodile.

"Poor guy." Raph breathed with a lot more sympathy than I usually got from him. And I could understand why he decided to show it now. This was horrible. No wait, it wasn't horrible. It was inhuman. I gave my brothers a gesture and we all ran out from our hiding place with our weapons ready.

"Freeze Savage! Turn the man back to normal, right now!" Raph looked at me with a deadpan look.

"Wow, Leo. That'll really make him run for his money." I ignored him and had my eyes set on Dirk Savage. He looked very surprised, but then started to smile evilly and pulled out a gun.

"Well would you look at that Abigail. We don't have to look for the mutants or create them, the mutants are coming to us. Take them down!" He pulled out another gun from his belt and started shooting nets with one and tranquilizers with the other at us. Abigail ran up to a desk and pulled out a long knife and attacked me and Raph. And I would be lying if I said she wasn't a good fighter. She was strong, fast and determined. But too bad for her, so were we.

Dirk Savage was fighting off Mikey and Donnie. And when Mikey was about to strike he shot out one more net he managed to capture Mikey in it. He rolled to the floor, tangled up in the net. Donnie ran up to Mikey and was about to help him when Dirk blocked his way and pulled out a army knife and tried to cut his throat open. Donnie barely had time to get out of the way before the knife met his skin and tried to sweep at guy's legs, only to get a kick in the head.

"Hang on Donnie!" I tried to get away from that Abigail, but she had also picked up a gun and fired a net at me and I barely had time to slice it with my katana before I rolled away from and her and over to Mikey and sliced the through the net holding him. Mikey flew up from the ground, called out a fast 'thanks' and then ran to help Raph, who was still holding of Abigail.

Donnie on the other hand could be better off. He was doing everything he could to dodge the nets, the bullets and the knife. And seeing how big and muscular this guy was, it wasn't looking so good. I ran up to him when I saw Dirk throw him into the ground and was about to stab him in the head. I ran up and kicked him away and I saw in the corner of my eye that he crashed into the wall, close to the purple mutagen. I walked up to Donnie and helped him to his feet.

"Are you okay bro? He seemed a little tough." He didn't answer. He was too busy trying to catch his breath, but did his best to give an answer.

"A li-little tough is a-an underst-statement Leo. But I'm fine, a few scratches but I'm- OW!" He cried out in pain and instinctively grabbed his right arm. A little dart was stuck into his upper arm, and some kind of fluid was in there, but it disappeared so quickly though the needle we didn't see what it was. I looked at Dirk and he held some other gun and I had a pretty guess he had fired the shot.

Donnie's first instinct was to pull out the dart and was about throw it into the wall, but changed his mind and put it in his belt instead. I guess he wanted to make tests on it. I looked over at Raph and Mikey, who seemed to have a hard time with Abigail. I put my fingers in my mouth and whistled loudly.

"Turtles, fall back!" Raph dropped his fighting stance and started to run away from the woman and grabbed Mikey's arm and dragged him along.

"I'll accept it! Let's move!" I was a little surprised that Raph agreed with me, but shock it off and we ran for the doors, ran through the corridor and jumped through the window and left the building in less than a minute.

* * *

(Abigail's P.O.V)

As the turtles ran away Dirk just stared after them and didn't even attempt to catch them. I looked at him in confusion, dropped the knife and walked up to him.

"I thought we were supposed to _catch_ mutants, why are you letting them escape?" He smirked darkly and turned to me.

"Oh, don't worry Abigail, we'll find them. I managed to hit one off them with a small amount of that mutagen. And if they are as loyal to each other as they seem, the others will do anything they can to help their friend. Either that or we'll find that freak and the others will find him as well. Forget mutating so many humans, these turtles will be enough to get enough attention from the people of the city, and even the world." I got confused. Wasn't that turtle already a mutant? Why mutate him further?

"But Dirk, he's already a mutant. Why would you want him to mutate even further? And the process will not be immediate. It could take a while before the effects happen seeing as another mutagen is in his blood." He smirked wider and raised one of his eyebrows in a cocky smile.

"Yes, I'm aware of that. But don't worry, it might take a day or two but once he is mutated and completely mindless, he'll be easy to find. And where ever we take him, those other turtles surely will find him. And when they do, they'll be mine."

* * *

(Raph's P.O.V)

We were all sitting in the living room and Donnie's was patching Mikey up. He had very quickly washed and wrapped a bandage around his arm and was now cleaning up Mikey's wounds and placed a band-aid on his forehead, where Abigail's knife had left a small mark. Leo and I hadn't been very hurt and Donnie had also managed to get out of the fight without too many wounds. But Mikey had managed to get a few off them. I put my hands on my shell and stretched out my back, trying to ease the pain.

"Ow, man these guys were better fighters than I anticipated. I blame it on fighting robots for so long I've forgotten humans can be pretty darn good fighters too." Leo nodded and rolled his shoulders and his neck and I saw he had spots that hurt.

"Yeah, tell me about it. I guess we didn't expect them to be as good as they were. If we run in to them again we'll be better prepared. Or else we'll be captured by them." Donnie was done with helping Mikey and was looking at a tube-looking dart, about as big a one of our thumbs and had a small needle in on end of it.

"Where did you get that? Have found something that could help us?" I was expecting an answer I wouldn't understand, but got slightly surprised.

"No, I mean I don't really know. That Jerk Savage shot it into my arm and I'm trying to see if there's anything left in it, but it doesn't seem to. From what I can tell it's empty." Mikey tried to look at it too, but didn't seem to find it interesting.

"Hm, it just looks like one of your darts in your lab. What's so special about this one?" Donnie just rolled his eyes and put it back in his belt.

"I don't know yet, but I'd like to know what that guy put into this thing, since it was stuck in my arm." He yawned and stretched his arms over his head. "But I'll make a blood test tomorrow. I'm so tired right now I could sleep on this couch." I nodded and yawned so big I almost thought my jaw would break.

"Me too, I'm exhausted." Leo yawned as well and stretched his arms over his head and let out a uh-uh sound. But Mikey suddenly grabbed Donnie's good arm and shook it slightly.

"But Donnie, what if there was some kind of sleep poison in that tube and once you fall asleep, you'll never wake up again!" He just sighed and jerked his arm away from Mikey.

"Don't be silly Mikey. If it was a sleep poison, I would be asleep by now. I'll figure out what it is tomorrow." But Leo grabbed his shoulder and held him back when he tried to go to his room.

"But why take the chance? What if it _is_ a sleep poison or something worse? Just a small test and then go to bed, what do you say?" But Donnie seemed to very annoyed and pushed his hand away.

"I'm telling you Leo, I'm fine. I'll take care of that test, _tomorrow_!" I could hear the suppressed anger in his voice and decided to try and to calm him down a little, before he exploded.

"Yeah Donnie, but don't you-" I didn't even get chance to finish the sentence before Donnie turned around and, call me insane, but his eyes looked like lizard eyes! A thin pupil and both the brown eye color and the eyes white had both turned amber colored. And I also heard his voice get a little deeper.

"Would you get off my back! I said I can check on it tomorrow, so would you all go to bed or at least annoy someone else, because you're really starting freak me out! I wonder why _I_ of all people in this would had to be stuck with such annoying, badgering, creeps!" He turned on his heel and marched over to his room, opened the door and slammed it shut.

The first seconds after his outburst I was more shocked than upset. Usually I wouldn't just stand there and listen to someone who insulted me, but Donnie never acted like that so I didn't really know how to react.

"So, that happened." Mikey said carefully and Leo put his finger to his chin in thought.

"I've never seen him so angry before. Sure, I've heard him snap, or lose his patience and such but I've never seen _that_ angry before." I looked at my brothers and decided to tell them what I saw.

"You know, call me crazy, but when he turned around to look at us, I could've sworn I saw his eyes change from normal to lizard eyes!" Mikey nodded eagerly and pointed at, as if I had made a good point.

"Yeah yeah, like one of those lizard monsters in those old horror movies they show on TV and such. It looked just like that!" Leo nodded too and I was glad I wasn't the only one who saw the change.

"Right, and did you hear his voice? It sounded like it had gotten deeper, didn't it? Or is that just my imagination or something?" Both Mikey and I shook our heads and Mikey placed a hand on his shoulder. "No way, dude. I heard it too!" I shook my head a little and for once tried to be reasonable.

"Look, we're all tired, and maybe Donnie snapped because he was exhausted. And the whole eye and voice thing could be our tired imagination? Let's all go to bed and see how things look tomorrow." Mikey looked like he wanted to stay up, but Leo shoved him towards his room.

"Right, good idea Raph. I'm sure he'll be in a better mood tomorrow." So we all went back to our rooms and got ready to go to bed. What no one of us knew was that in Donnie's room was Donnie lying in his bed and held in arm as burning pain was running through his veins. And neither did we know that things would only get worse. A whole lot worse.

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**A/N: Okay, I feel the enemy plot is really lazy, but again it's not going to be much about that plot. It's more about the turtles. I really hope it's acceptable and that you can read it okay. And again, in less than two weeks I'm going back to school, so I maybe not update as usual as I would like. Please don't hate me for it, and now the harder parts a over, and hopefully I don't have many hard parts left. Hope you enjoyed it and please follow, favorite and review. G'night everybody! **


	3. Chapter 3, Stronger, faster and weirder

The monster underneath the surface

**A/N: Alright, IT'S FINALLY UP! I'm trying to update faster, and so far it's not going very well, but I have something I want to ask you. I know I said in my AN before that I planned on making a TMNT AU after this story, but now I've gotten inspiration for a new TMNT – Frozen story, which will probably be last one in that series. So I want to know, what do you want me to write first. AU or new frozen? Tell me in your reviews or in a PM.**

Chapter 3, Stronger, faster and a lot weirder

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(Donnie's P.O.V)

I woke up when a sharp wave of pain flew through my arm and I sat up and grabbed my upper arm. The pain only lasted for a few seconds but when I removed my hand I saw the bandage had fallen off and around the small wound, where the dart had been stuck, a purple color was decorating my skin. It looked like a bruise.

"Hm, it must've hit a vein or something." I muttered to myself and looked at the alarm clock and saw it was about 7 AM. Mikey should be up by now to make breakfast. And that meant the other would be awake too. First then did I remember what happened last night. I lost control and yelled at their faces and I could be wrong, but I felt like something took over me for a few seconds. But it disappeared so fast I barely had time to notice it. And for at least an hour after I had felt a sharp pain in my arm. But anyway I would have to apologize for my behavior last night.

I removed the blanket and was about to get up but then I realized I had been sleeping with my knees against my chest and my arms crossed and my chin on top on them. Kinda like a dog. Why had I slept like that, I've never slept like that before. I also realized I felt a lot more energetic and psyched than normal. I feel like I could take on anything or anyone, which was very new. I literally _jumped_ out of bed and tied the mask around my face and placed the gear on my knees and elbows in less than twenty seconds and ran out my room... and crashed into Leo. Both of us fell to the floor and I heard Leo gasp for air as he was knocked to the ground with me on top of him and at first he looked confused, but then smiled a little.

"Are we in a hurry today Donnie? It's not like the breakfast will walk away, right?" I chuckled nervously and climbed of Leo's chest and offered my hand to help him up, which he gratefully accepted.

"Sorry, I wasn't looking where I was going." Leo just shrugged it off and that was all I needed to know he wasn't angry. Good thing it was Leo I crashed into and not Raph. Leo gripped my arm a little firmly and seemed to look for something or examining it.

"Wow Donnie, you seem to have gotten stronger. I guess the combat with Savage helped out a little." I rubbed the back of my head and chuckled a little. I felt nervous and tried to find the right words. I wanted this to sound good and not something I felt like I had to say because it was the right thing. It had to come from the heart.

"Uh, Leo. About last night when I, you know, lost my temper like that?" Leo nodded and his smile disappeared, but he looked more curious and concerned. I took a deep breath and continued to talk, before I got nervous again.

"I just wanted to say that I'm sorry about that. I don't know what came over me, I guess I was tired and I kinda lost it so, sorry." I looked up at him and he smiled lightly at me and wrapped his arm around my shoulder.

"Hey, it's alright. I guess everyone needs to let anger and frustration out every now and then. Just, next time try to do not to yell at our faces. It's bad enough that Raph's way of letting out anger is by yelling and fighting." I giggled a little and we walked to the kitchen. As I had assumed Mikey was up and was at the moment making breakfast at the stove, and Raph was reading a comic at the table, waiting for the food to be finished. Leo sat down beside him and I sat down beside Leo.

"Hey Mikey, how are you doing? Will the food be finished soon?" Mikey took a wood spoon and waved it in a warning way.

"Will you chill already? It'll be done in a minute, okay? Just chillax man." Leo raised his hands in a sign of peace. I wasn't surprised to see Mikey react this way. When it came to cooking, Mikey wanted perfection, even if sometimes his way of creating perfection was a little scary. Like his P-shakes, his own pizza he made not so very long ago. Ugh, the mere thought of it was enough to make you want to puke. I mean, how did he not notice a _rat_ had managed to get into the pizza dough?

"_But, then again it was a rat. And rats are usually very clean creatures. I mean, they avoid swimming just so they don't have to fix with their fur. Just like a cat. So, what if it was okay to eat it. I mean, Mikey could keep the pizza, but the rat..."_

"Dude, you're drooling all over my comic!" I was pulled out of thoughts and realized Raph was yelling at me, and he was right. I had started to drool and some of it dripped on Raph's comic. But I quickly wiped the saliva from my chin and denied Raph's words.

"What? No I'm not, there's a leak in one of the pipes or something." Raph rolled his eyes. He knew I was denying it and just put away the comic book as Mikey came up with plates with omelets on.

"Here you go bros. Hot, newly made pizza omelets." The others started to eat with good appetite, but I was thinking over the thoughts that had entered my head before. I was actually thought of eating a _rat,_ and started to drool as well! What the shell is wrong with me? And I also realized as I ate the omelet that it didn't taste as good as it used to be. But others didn't complain so I guess it was just me, but why? I usually didn't have anything against Mikey's pizza omelets. In fact, it was really good. And Mikey noticed I didn't eat as much as the others did.

"Donnie are you okay? You're not eating. Is something wrong with it?" Leo and Raph looked up from their plates too and looked at me. I knew Mikey was sensitive about his cooking and I didn't taste anything _wrong_ with the omelet, it just didn't taste as good as it usually did. So I put a smile on and tried to look reassuring.

"No, Mikey. Nothing's wrong, I just-" I was interrupted when Raph screamed high pitched and flew up from the table and the rest of us jumped in surprise. Then, and it went by so fast I almost didn't know I did it, I reached out and grabbed something from Raph's plate and had whatever it was in one of my hands and the other hand over that hand to keep in from escaping. Both Mikey and Leo looked at me with wide eyes, but Raph didn't mind, he seemed to be pleased that the little nuisance was gone from his food.

"Whoa, Donnie. Nice reflexes you got there. Have you been practicing?" I didn't answer I just opened my hands slowly and pressed my face down against my hands to see what it was. And for some reason I also sniffed into my hands, but I saw what it was so it was rather pointless.

"It's just a little cockroach. Nothing to be afraid of Raph." I opened my hand and took the roach with two fingers and felt the small legs brush against my skin as it tried to get away from my grip. But Raph still kept his distance from me and the roach. Leo seemed a little disgusted and had a frowned at it. Mikey just looked at it, with a small smile on his face. He then turned to Raph and smirked at him.

"Aw, don't worry Raph. Donnie has the little roach now, you don't have to be scared anymore."

"Oh, I'll show you scared Mikey! When I'm done with you even Shredder will be scared to see you-" I heard Raph starting to yell at Mikey and that they started to run around and assumed that Raph was chasing him, but his voice started to fade away and I only heard a few words or screams here and there. All of a sudden I got that feeling again that something was taking over my brain. And every ounce in me fought against what my brain told me to do, but it got ignored. And before I even realized what I did, I threw the roach in my mouth and chewed on it and swallowed. And once I threw it and and closed my mouth, I heard yells in disgust.

"EW! Donnie what are you doing, that's nasty!" Leo yelled at me and I turned at him and saw that both Mikey and Raph had stopped wrestling and stared at me, Raph had his hands over his mouth and looked like he was about to puke and Mikey had wide eyes and a sealed mouth. But my brain was still not working the way it was supposed too, so my mouth was talking but I wasn't sure I meant any of the things I said.

"What? Did any of you want it?" Leo looked horrified and raised both hands in front of himself and his eyes was wide and his pupils was tiny.

"NO!" He cleared his throat and took a deep breath. Mikey looked at me and had a big frown on his face.

"Dude, what is wrong with you? I get that you guys think my cooking can be crazy, but it's not so bad that you have to _eat_ roaches to survive." Raph didn't say anything, but I saw that he wanted to puke. I saw Leo tried to stay calm as he placed a hand on my shoulder. But I saw he wanted to freak out.

"Donnie, you do realize that you just ate a cockroach, right? You _ate_, chewed and _swallowed_ a _cockroach_! And cockroaches are known to have disease and nasty germs and- Ew!" I just shrugged his hand off and stood from the table and dumped the rests of my food in the garbage.

"Well, they're good snacks. And they taste better than those omelets, no offense Mikey, and now if you excuse me, I am going to the dojo to warm up. See ya at training." I left the kitchen and it wasn't until I entered the dojo that I really realized what happened, I actually ate a roach! And the biggest shock was that I really didn't mind. It didn't freak me out or made me feel disgusting. What is happening to me?

* * *

(Raph's P.O.V)

When Leo, Mikey and I entered the dojo we saw Donnie doing some exercise with his bo staff. He had his eyes narrowed and seemed to be deep concentration as the staff was spinning around in a circle between his fingers. Sometimes he spun the staff around himself, made a strike against an invisible enemy or moved from spot to spot while spinning the staff or making an attack. But he still noticed we entered and stopped doing what he was doing and turned to us. He didn't smile, in fact he decided to keep his distance. And I also tried to stay away, I mean he had just swallowed roach! Not exactly something I wanted to be reminded of at the moment.

Master Splinter walked out of his room and walked up to us. We immediately got in line and kneeled down in front of him. He looked down at us and then told us to stand up.

"My sons, the dangers in this city have been growing during the last year and I want you to never lose focus on that. You must always keep your focus and never lose sight on what is important. Do you understand?"

"Hai Sensei!"

"Hai Sensei!"

"Hai Sensei!"

"Hai Sensei!" Splinter looked at all of us, but then took a look at Donnie's arm. He saw the white bandage and his eyes narrowed in concern.

"Donatello, what happened? How did you get that wound?" Donnie looked down at his arm and shrugged a little at the wound. I saw he was trying to hide something, but I couldn't quite put my finger on what.

"I-it's just a little bruise Sensei. It's nothing, a little Tylenol and it'll heal in no time." Splinter didn't look convinced as he took Donnie's arm and unwrapped the bandage and revealed a big, nasty and dark purple bruise. Leo, Mikey and I looked at it with wide eyes and even Donnie seemed surprised with what he saw and again he saw he was trying to suppress something but I didn't see what. Splinter showed no real emotion, he just let go of Donnie's arm after he wrapped the bandage back on again.

"How did you get that bruise Donatello? What happened last night?" Donnie looked to the floor and when he opened his mouth Mikey interrupted, trying to be honest or whatever.

"When we were on patrol last night he got hit with a dart, maybe that's what caused the bruise." Donnie snapped his face in Mikey's direction and had pure anger in his eyes.

"Thank you _Michelangelo_. I don't know how I could've answered that question without your ingenious help. _Thank_ you _so much_ little brother." Mikey flinched a little at Donnie's rudeness and choose to back off. Donnie almost had the same anger he had last night, but no quite. Splinter placed a hand on his shoulder and almost shoved him towards the door.

"Perhaps you should see if there is anything dangerous in your body, just to be safe. I don't wish for one of my sons being in any kind of danger." Donnie looked surprised, and then got a little angry again.

"But Sensei, I'm fine. It's just my arm, and it doesn't even hurt. I can train now, it's fine, I won't get problems because of a bruise." I couldn't help but roll my eyes and scoff at his words.

"Huh, maybe it'll help us beat you faster so training can be over faster." And the next scene went by pretty fast. Donnie looked in my direction and for a second I saw those lizard eyes again and then they disappeared again.

"Oh yeah? Well, I'll show you who's easy to defeat!" And then he flew on me, knocking me to the floor and I didn't even have time to recover before he had pulled out his bo staff and tried to hit me in the head. I rolled out of the way and tried to roundhouse kick him in the shell, but he did a somersault and tried to sweep my legs. I did a backwards flip and tried to punch him, but he just grabbed my arm, flipped me to the ground and then sat down on my chest and pinned my hands to the floor and held me there. I tried to fight back, which normally would have been easy, but somehow Donnie had gotten stronger and faster than last night. After a few minutes of struggling I gave up and looked up at Donnie, who looked both firm and angry.

"Ugh, how did _you_ get so strong?!" I heard my voice crack a little and usually I would try to hide it but now I was focusing on something else. Donnie narrowed his eyes and tightened his grip and my wrists and pressed his legs closer to my sides.

"I don't know, how did _you_ get so freaking annoying?" I felt anger boil in me and tried to get up from the ground, but Donnie's grip tightened so much it actually hurt. It took both Leo's and Mikey's strength to pull Donnie off me, and it wasn't easy I could see that. Leo grabbed Donnie's shoulder and shook him a little.

"Donatello, I don't know is going on right now, but whatever it is making you act like this has to stop! It's one thing to yell at us every other blue moon, but it's not okay to attack people like that! It's bad enough that Raph does it all the time, but I don't want to see you do that again!" Donnie just glared at Leo while he was speaking, then he yanked his arm away from Leo and pushed him in the chest, making him stumble backwards.

"Oh buu-huu! Our fearless leader can't have things the way he wants them to be! Isn't that just sad? A tragedy really, somebody oughta give him a hug, or maybe a little kiss to make it all better again!" No one said a word. It was so rare to hear such anger and frustration from Donnie of all people, no one really know how to react. Donnie turned to Sensei and looked a little less angry.

"You know what Sensei? It might be a good idea to go the lab for a while." He walked towards the exit, but on the way out he stepped on my chest, just as I was about to stand up, and made me lose all air in my lungs and knocked me back to the ground. The rest of us watched him leave the dojo and we all shared the same thought.

_"What the heck is happening with Donnie?" _

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**A/N: Oh, tension is building up. What is going on and what's going to happen next? I hope I can update at least one more time before Monday, after that I'm going to high school. From then on I will update as often as I can. And please favorite, follow and review and also be nice to give your opinions about what story I should do after this, cause right now it's a tie. G'night everybody!**


	4. Chapter 4, Transformation

The monster underneath the surface

**A/N: Yay I did manage to update, although not before school! I've noticed that this story has been harder to write than I thought and since school has started I might not update as quick as I would like, so please try to have patience, I'm doing the best I can. Please review.**

Chapter 4, Transformation

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(Mikey's P.O.V)

This day had started out kinda normal. I had made a great breakfast, Raph had been his usual morning tired self and Leo had also been rather normal. But then things had gone from normal to crazy weird in less than two minutes. First Donnie didn't like his omelet as much as he usually did. Normally he could eat my pizza omelets without problems but today he said it didn't taste as good as it usually did. Then Raph had freaked out over a roach and Donnie had grabbed it so fast it seemed inhuman, or inturtle or whatever. And then he ate it! And didn't even seem disgusted by it. It seemed like it was something he always did or everyone else did. And he also managed to beat Raph in the dojo and _acted_ like Raph too. He was both rude and sarcastic, which was not something we knew how to deal with. An angry Raph was one thing cause we have been dealing with that since day one. But Donnie was never acting like that. Right now we were all sitting in the living room, talking about what to do next.

"Do you think all the time in the lab creating that retro mutagen has messed up his brain or something?" Leo shook his head and placed his chin in his hand and rested his elbow on his knee. He looked troubled, that was plain to see.

"No, it can't be that. I mean, he only started to act like this today. It has to something else. What drives me crazy is that I can't figure out what it could be!" Raph had his arms crossed over his chest and leaned against the arcade game with a frown on his face.

"You think it was that dart that made him act like this? Maybe it's a side effect of whatever science goo was in that dart?" Leo rubbed his chin and nodded a little. It did sound likely, I mean what else could have made Donnie act like this? We hadn't done anything, I think.

"Yes, it would make sense. But whatever was in that dart couldn't just have been created for making people act like Donnie does. When Dirk mutated that guy it happened immediately, so why hasn't any other effects happened?" I shuddered and hugged my arms.

"Ugh, I'm not sure I want to know what could happen if even more crazy stuff happened."

"What could happen?" We all turned to the turnstiles and saw both April and Casey walk in and April had her school bag over her shoulder and Casey had his golf bag with his own weapons. April, who had asked the question, looked both concerned and a little on her guard. Leo sighed and put his face in his hands. Raph looked at our friends and answered for Leo.

"Donnie has been acting really strange all day, and we think it has something to do with what happened on a mission last night. We were checking out this Dirk Savage guy and while we were there Donnie got a dart in his arm and ever since last night, just before we went to bed, he's been acting really weird." April dropped her bag and walked over to the couch and sat, with Casey right behind her.

"What do you mean 'acting weird?' I mean, has he been drained of all his brain power or something?" Casey said that with a smirk and it was clear he didn't take himself seriously. Leo shook his head at him with a small frown. But I saw he was a little more worried than irritated.

"No, man. He's become distant, short-tempered, stronger and faster, and he's even become kinda disgusting. Today he picked a fight with Raph and _won_! And he's got a lot more attitude and yelled at me and snapped at Mikey. I don't know what's going on with him, but I don't like it one bit." April frowned and hummed in thought, but Casey asked about something none of us wanted to answer.

"Well then, what did you mean when you said he's become disgusting. Did he forget to shower or to put on deodorant or something?" I guess he was trying to make a joke, but right now it really didn't fit. Not even I felt like hearing a joke or even telling one.

"No, not that kind of disgusting! When we had breakfast today Raph got scared when a roach walked all over his plate." Usually I would hear Raph saying he wasn't scared but not this time, so I continued. "Donnie picked up the roach, with super reflexes by the way, and after a minute he _ate_ it! Just like that, and he didn't even pretend to puke or shiver in disgust! Whatever is going on it's both creepy and nasty!" April's eyes widened in disgust and surprise and covered her mouth with her hand and Casey looked like he was ready to puke any second.

"Seriously? He ate it? Just like that? Ew, that's just wrong!" April half yelled in disgust. Casey nodded and walked up to Raph and placed his arm around his shoulders.

"Yeah, bro. I mean, I knew Donnie can have his weird moments and could act really crazy, but this takes the cake! What the heck have you planned on to stop this weirdness?" Raph threw Casey's arm off him and walked over to the couch and sat down.

"I don't know, we're kinda thinking about what to do next. What do _you_ say fearless?" Leo glared at the nickname, then shook his head slightly and rested his head in his hands.

"I don't know, I- I just don't know. I mean I have no idea on how to deal with something like this." While the rest of us continued to discuss on what to do right now, I saw April walk towards the lab and peeking through the almost shut door. I was about to stop her but decided that maybe she could help Donnie a little. After all, she was his best friend. And besides, if April couldn't get through to Donnie no one could.

* * *

(April's P.O.V)

As I listened to the guy's conversation I heard a strange sound, like when a cat or a dog catches a rat or a bird and walked up the lab door while the others kept on talking and peeked through the small crack between the wall and the door just in time to catch Donnie slurp in a rat tail like it was spaghetti into his mouth. I couldn't help but shudder in disgust, and apparently Donnie heard that and before I could react he ran towards the door opened it up a big more, grabbed my arm, pulled me in and then slammed it shut with a 'SLAM' and then let go of my arm. It all went by so fast and all I could do was yelp in surprise when he grabbed me.

When he had closed the door he turned to me and I immediately saw something was wrong. His eyes seemed different, kinda like a lion or a tiger that studying its enemy before attacking and his body language was also a little different, again kinda like a predator on its guard. And when I heard him talking he sounded different too.

"What were you doing? Spying on me, or maybe just looking at how 'strange and weird' I'm acting, or what was it my brothers said?" I got a little confused and tilted my head to the side at him and tried to ignore the cold stare in his eyes.

"How did you know what they said? The door was almost closed and it looked like you were in the middle of something. Did you eavesdrop on us?" He growled, and even that sounded more animal-like, and took a few steps forward and I found myself backing away from him a little.

"No, I heard them through the door. My hearing has increased at least threefold, I've heard everything even if I didn't want to hear it. Now, I wanna know why you were spying on me! Trying to see if I am as stark raving mad as the make me sound like?" I was taken back by both the force and the accusation in his last sentence. I shook my head and put up both my hands in a defensive gesture.

"Your brothers never said anything about you being stark raving mad." His face showed nothing but anger and he almost yelled at me now.

"They didn't have to. I get the picture without them telling me what it's supposed to be." I stepped forward and placed both my hands on his shoulders and I felt how tense his muscles was.

"Donnie, no one is saying you're crazy. Your brothers are worried about you and wonder why you act like you do. We just want to understand, that's all. So please Donnie, tell me what is going on?" I saw his eyes both widen and his glare got a little softer and then he put his hand to his forehead with a small grunt, as if he had a headache. He took a deep breath before sitting down at his computer chair and put his face in his hands. He sighed and looked down at the floor.

"It's not my fault. Ever since last night I've been feeling different. Like someone is inside my head and sometimes take over my mind and makes me act weird. Sometimes I remember what I've done and other times it's nothing but a blur. I know it sunds crazy but it's the best way I can explain it. I've been trying to do tests on myself all day but I just can't concentrate. I know something is happening to me, but I can't figure out what's going on." He reached over to a small bowl and picked up something brown and round and put in his mouth and swallowed it, but he didn't look like he enjoyed it. I walked over to the bowl and tried to identify what was in it.

"What are you eating? Some kind of candy or something?" He looked over at me with a look of disgust and grabbed my wrist and pulled it away from the bowl when I tried to pick one of the brown things up to identify it.

"It's roaches." I let out a shriek of disgust and stepped away from the desk and put both my hands over my mouth and gagged into my palms. When I was done I looked over at Donnie and I knew my face looked like a question mark. He looked disgusted but picked up another one and ate it.

"I really hate it but I can't stop eating. About an hour ago my brain kinda shut off and I walked out into the tunnels and started to find roaches and killen those I found and put them in this bowl. And I also got a few rats. I hate what I'm doing but I have no control over myself." I felt a pang of sympathy and walked up to him and put a hand on his shoulder.

"Don't worry Donnie. Whatever it is we'll work through it. We'll help you and do what we can, don't forget that." He looked up at me and smiled lightly at me.

"Thanks April. I really appreciate it." I smiled at him, but suddenly I saw something that made me draw back my hand and take a step away from him.

"What's happening with your nose?" He looked a little confused and brought his fingers up to his nose and touched it, trying to feel something wrong.

"What do you mean? What's wrong?" But what I saw was a little too scary, not to say strange, I just couldn't respond. His green skin had started to change color, from olive-green to a dark shade of purple. And from under the bandage on his arm the purple started to spread as well.

"What is it April? What's happening to me?" Donnie asked again and this time I tried to come up with a good answer. What on Earth was I supposed to answer? 'Hey Donnie, your skin is changing color from green to purple, but don't panic we'll totally fix it?' But I decided to be honest.

"Donnie, your face, your skin, you're turning purple!" His eyes widened and looked down at his arm and saw the color spread from his arm to his shoulders, neck and his other arm. He looked like he was about to freak out. I walked a few steps away from him in shock and a little fear. Donnie flew up from his chair and just watched as the purple color spread to his legs and feet.

"What the heck is going on here?!" He asked, more to himself than to me. I didn't know what to say, but I tried to keep a little distance. I didn't know what was going on and I didn't want to scare Donnie even more. But then the real freaky stuff started to happen, and I had no idea if I should try to be sympathetic or horrified.

Donnie's muscles, who usually was nothing compared to Leo's or Raph's, started to grow as well as his whole body. His knee pads and elbow pads ribbed and fell to the floor as well as his belt and the strap over his back. And he was now so tall I guessed he was at least 8 feet tall now and his eyes had changed from brown human eyes to some creepy lizard eyes with thin pupils and with red-orange instead of brown. On his fingers long sharp claws started to grow and his mouth was now full with sharp teeth as well. And during this transformation Donnie had shown clear signs of pain. He gripped his head with a grunt of pain and looked at me with pain and fear written across his face. I stared at him with a wide open mouth and wide eyes and my body was frozen and I couldn't move a single muscle.

"Run." He hissed at me. His voice had gotten deeper and scarier and it made my skin crawl. Usually I would want to stay and try to help in any way I could, but I realized there was nothing I could do right at the moment so I snapped out of my trance and ran for the door, ripped it open, ran out and then slammed it shut. But I heard muffled roars of anger and something was slamming against the door and I had a feeling it wouldn't stop him for long.

* * *

(Leo's P.O.V)

We were all so deep into our conversation we hadn't noticed April had disappeared into Donnie's lab. It wasn't until we heard the door slam against the wall that we turned around and saw April in panic running up to us. She was pale and her blue eyes was full with fear and confusion. And from the lab we heard some kind of roars and something was slamming against the door. April ran up to us and almost tripped over her own feet.

"Guys, we have a terrible problem!" We all ran over to her and Casey wrapped his arm around her shoulders and tried to calm her. But she didn't seem to notice him at all, she was busy trying to catch her breath, so I put my hand on her shoulder and talked calmly to her.

"It's alright April, calm down. Take a deep breath and tell us, what is going on? What is so terrible?" April took a few breaths before shrugging Casey's arm off and then pointed to the lab which now had gotten so quiet it was a little unsettling.

"It's Donnie, he has a huge problem!" Mikey placed his hand on her shoulder and patted it before he pulled his hand back again.

"Yeah, we've kinda noticed that April. We know has been acting weird today, and I don't think it's so bad that you can call it terrible." April shook her head with a little more force than necessary and her headband flew to the ground, and pointed to the lab frantically.

"No, no! I'm mean a _really_ _terrible_ problem, he's turning into a monster!" Raph shook his head a little and placed a hand on her back and looked at her with a serious look.

"April, we know Donnie's been acting really strange but I think calling him a monster is a bit of an exaggeration. A few nasty habits and a little more attitude doesn't make someone a monster." That was a little weird, coming from Raph, but I decided not to bring it up. April shook her head with so much force her ponytail loosened and her hair fell down her shoulders.

"No, no, _no_! I mean it! He's actually-!" She was interrupted as a loud crash was heard and no one said anything or even breathed too loud and I saw the lab door was now forced open and a little damaged. Nothing was heard for a long time, but after a few minutes a small sound of foot steps was heard above our heads and we all looked up at the pipes in the ceiling but saw nothing. And then, just to fit the situation I guess, the lights flickered and then turned off, leaving us in almost complete darkness. April's eyes widened and she looked back at us again.

"He got out of the lab." She whispered and you had to listen really good to hear it. Mikey turned to April and hid behind her.

"So, uh what _did_ you mean when you said Donnie is turning into a monster?" He sounded like a little scared and worried child and Raph walked up to Mikey and smacked him across the head.

"Donnie is _not_ a monster Mikey! He's probably just trying to scare us or something. He was kind of a jerk before, so why wouldn't he be a jerk now?" Casey nodded firmly and placed his hand on his puffed out chest.

"Yeah, and can tell you right away, that no matter how weird, strange or even bizarre he's acting or no matter how much of a jerk he is now, I will never, ever be scared of Donnie." He had barely finished that sentence before something landed on the floor behind us and we all froze in our places. April and Mikey stood in front of us saw what was behind us and was both pale, had their mouths open and disbelief in their eyes, so Casey, Raph and slowly turned around to see who or what it was, and the sight will never leave me for as long as I live.

In front of us was a creature, at least eight feet tall, had big muscles, long, sharp and deadly claws on both feet and hands and sharp teeth in its mouth. The skin was a dark purple color and in this light it almost looked black and the shell looked like a dark mix between black and grey and at the shoulders it looked like spikes had been formed. A long tail was swaying behind him and at the tip there was spikes that also looked sharp and deadly. And on the head was something that looked like a mohawk but I could see it was also very sharp. Kinda like claws on the head. But it was the eyes that caught my interest. Eyes that once had been full over curiosity, love and knowledge was now full of pure, unadulterated rage and had on sign of humanity whatsoever. It didn't take long for me realize who it was.

"Donnie." I head April whisper and in response the monster before us growled and didn't seem to recognize his name at all.

"No." I whispered and looked straight at the creature that once had been my genius little brother showed no similarities with Donnie at all. Raph shook his head in denial and muttered 'no' over and over to himself and I heard Mikey whimper a little. April turned to Casey, who was looking terrified and stared at Donnie and she hissed at him, making him snap out of his trance.

"You were saying, tough guy?" And just as soon as she finished that sentence, Donnie let out a loud roar (that I swear I recognized from a Godzilla movie) and then he attacked.

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**A/N: Okay, so it's finally up. I will try to update every weekend cause, as I've said before, I'm back in school. So have patience. And about the design of Donnie's mutation, well use the link bellow to see the picture I used for inspiration, or just go to deviantart and type in Dark Donnie 2k12 style, but I have left out a few things obviously. Anyway, good night, thanks for waiting and please favorite, follow and review. **

** art/Dark-Donnie-2k12-style-398664909 **


	5. Chapter 5, What are we going to do?

The monster underneath the surface

**A/N: Okay, here is the next chapter, on a weekend like I said I would be uploading on! Okay, So I'm a week late, but here is my excuse. I know this chapter is a little bit shorter than my usual chapters but I didn't have that many ideas on how to write it and I had a busy weekend so I did the best I could, I really hope it's good enough for you, I will have to think over how to continue this story. **

**But anyway, I hope you enjoy the chapter and please be so kind to leave your reviews and favorite and follow this story.**

Chapter 5, What are we going to do?

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(Raph's P.O.V)

For what felt like an eternity I didn't know what to think. The creature in front of me with long claws, sharp teeth and purple skin was supposed to be my little brother Donatello, I mean it was just so hard to believe. But then I forced myself into thinking again when Donnie went down on all fours and ran towards us with a roar.

"Look out!" I turned to Mikey and pushed him out of the way and shoved April's shoulder to make her move and then jumped out of the way myself. Leo grabbed Casey's arm and pulled him away while he ran out of the way. Donnie set his eyes on me and started to chase me around the lair. He was a lot faster than he had been this morning and was only a few feet away from me.

"Donnie, stop it! It's me, Raph!" Donnie either didn't understand what I said or he ignored it, because he jumped with his arms stretched out and landed on top of me, forcing me to the floor,and tried to bite my head of but I grabbed his wrists and tried to push him away from my face. And now I got a better of his face and I saw he wasn't completely mindless, I saw some kind of 'humanity' in his eyes and he looked like he could think, though it was very, very faint. I managed to move my legs in under him and placed my feet on his chest and kicked him off me.

"I'm sorry bro, but you're out of control right now. Let us help you." Donnie had landed on the floor a few feet away from me and lowered his head a little, before growling and ran to attack Leo instead. Leo instinctively reached for his katanas but hesitated for a second. I saw in his eyes he didn't want to hurt Donnie, but was forced to draw his weapons and block Donnie's attack and then kicked him away. He had managed to swipe one of the blades over Donnie's left eye and it felt a short but bloody scar and the red blood looked kinda creepy with the dark purple.

"I'm really, _really_ sorry Donnie, but you give me no other choice!" Donnie growled again and stood up on his feet and gazed at us with pure rage. Then he caught me of guard when he opened his mouth again.

"It is useless to fight! I know all your strengths and weaknesses, give up now and I _may_ make your demise a little less painful!" Leo and I exchanged surprised glances and Leo leaned in closer to my ear.

"He's not completely mindless. He still knows who he is and who we are." I nodded and looked back to my deformed brother. Mikey had brought out his nunchucks, but he looked like he wanted to cry and he had his puppy eyes which made him look like a kicked puppy.

"But Donnie, we're your bros! I don't want to fight you!" Donnie growled threateningly and his tail was waved around dangerously and the pointy spikes on the tip looked so sharp it was scary.

"Tough titty." I almost dropped my Sai just as I had brought them out, I had never heard Donnie talk like that. He never used a dirty language, or dirty words for that matter. Casey put his mask over his face and took his baseball bat and raised it over his head ready to fight back and April reluctantly took out her Tessen and unfolded it. I could see she didn't want to do this, and I understood her. I didn't want to fight Donnie either, but at the moment we didn't have a choice.

Donnie made his move and swiped his tail at Mikey's head and managed to scratch the skin, shallowly but still. Mikey cried out in pain and dropped his nunchucks and gripped his head and that gave Donnie the upper hand and he sweeped his legs, making Mikey fall to the ground. I dodged his tail and tried to jump on him so I could hold him down, but he just grabbed my legs with his tail and threw me into the wall. But then Donnie turned to April and went down on all fours again and ran towards her with claws ready to tear her apart but Casey ran up to him and smashed his baseball bat against Donnie's head, making him fall to the ground and grip his head.

"Stay away from her, you freak!" April turned to Casey with anger in her eyes and Leo took the bat from him like a mother would take away a toy from a child who was breaking things with it.

"Casey, he's _not_ a freak! Remember, that's _Donnie_, _our_ brother! Do _not_ hurt him!" Then both Casey, Leo and April had to jump out of the way when Donnie attacked again and Leo had dropped the bat so Casey ran up to it and grabbed it again. I reluctantly grabbed my Sai but for the first time in my life I didn't feel like fighting back against the 'threat.'

"I don't think that's going to be a problem Leo!" Mikey had gotten up from the floor but didn't have his weapons, instead he left them on the floor. He raised his hands calmly and talked soothingly.

"Donnie, please listen to me. I know you're not yourself right now, but we can help you. We can figure out a way to change you back to old, nice self again. Just please, let us help you." Donnie seemed to think it over a little, then he roared again and swiped his claws over Mikey's face, leaving behind two long scars over his right cheek. Mikey cried out in pain, but before anyone could do anything else, another voice joined the conversation.

"What is going on in here?!" All of us turned to the entrance to the dojo where Master Splinter stood with a somewhat angry expression on his face. But when he saw Donnie I saw some kind of surprise and realization in his eyes. I saw him drop his stern and steady exterior and almost fell to the ground. Donnie saw that too and made his move. He went down on all four again and ran towards him. Mikey looked scared and saw that Sensei didn't see a monster, he saw his son and yelled to snap him out of it.

"Sensei, look out!" Splinter jerked a little and swung his staff at Donnie's head and he fell to the ground and groaned in pain. Splinter turned to us and looked both heartbroken and demanding at the same time.

"Boys! Get the chains, now!" I realized what he meant and immediately I wanted to protest. This was my brother not a monster, I didn't want to chain him up like one.

"But Sensei, it's Donnie!" I heard my voice crack a little and silently cursed over it. Sensei looked a little harshly at me and snapped when he answered.

"I know my son, but at the moment we have no choice! Get the chains, now!" Leo and Mikey ran towards the lab, where Donnie kept the chains along with other kinds of equipment and soon came back with the chains. Donnie had started to get back up on his feet again so I jumped on top of to try to keep him down and it did work. I had my knees on his elbows and sat on his shell, making it hard for him to move and Splinter helped me to hold him down, since he was stronger than before. While we did that Mikey and Leo wrapped his squirming wrists with the chains and tied the other ends to the big, thick stone pillar at the entrance and when both ends was tied tightly both Splinter and I jumped out of the way and out of reach of Donnie's claws and tail.

April and Casey, who had decided to stay in the background while we handled Donnie, walked up to us and watched as Donnie struggled against the chains and both roared and screamed angry words at us.

"Let me go and fight me! Fight me, you cold-blooded, spineless, loathsome cowards! Or you do chicken to fight someone who actually can fight back, you hideous freaks?!" Mikey buried his face in Leo's chest and I heard him sob lightly, and Leo placed his arm around Mikey's shell and let him cry. Leo looked crestfallen and I saw he also wanted to cry but held it back. April also looked ready to cry, but when Casey tried to put his arm around her she pushed him away and folded her arms over her chest, as a way of saying 'don't touch me right now.' Splinter's ears showed that he was sad, and even his face showed his sadness, which was kinda new, since he didn't always show emotion. I tried not to show any emotions, but I knew I showed at least some sadness.

"What are we gonna do now?" April's voice cut through the tension between us and Donnie, who wouldn't stop yelling at us. But his voice continued to mix in between roaring and yelling in a more 'human' way. Casey turned to her and pushed his mask up again, revealing his face.

"What do you mean 'what do we do now' Red? What _can_ we do? We're not geniuses, and we have no idea what to do now or how this happened, so what can we do?" April turned to him harshly and shoved him in the chest.

"Casey, do you have any idea how you sound right now? You sound like you don't even want to try to help the slightest! Fine, if you don't want to help us try to help Donnie go ahead and leave!" Mikey walked up to them and pushed them apart.

"Guys, please stop fighting. It's not helping the moment. But April is right Casey, we have to help Donnie! He's our brother, he would do the same for us if it was one of us!" Casey turned to Mikey and placed a hand on his shoulder.

"Yeah, I know Mikey. But what I mean is, _what_ can we do? I mean, Donnie's the brainiac of the team. He would know what to do, and I don't know about you but science stuff is not exactly my field of expertise." Leo closed his eyes and took a deep breath through his nose before walking up in front of all of us.

"Then we'll find a way. We have to! Donnie never stopped trying to help us because the odds was against him, so I'm not willing to give up on him now, so who's with me?" He reached out a hand for us and looked up at us. I took a breath and put my hand over his.

"I'm in." Mikey and April walked up to us, and Casey followed only seconds after seeing the others choosing.

"I'm with you bro."

"Count me in."

"Me too!" Splinter looked at us with a small smile, but then turned back to Donnie who was still yanking on the chains and he didn't look the least bit tired.

"Donatello. I know you are not in your right state of mind right now. Please, try to fight the monster in you and come back to us. We can help you, but you have to let us." Donnie had looked up when Splinter talked to him, but only snarled as a response.

"Never! If you have any spine, set me free and fight like a man, or are you too chicken to fight old man?!" I saw the shock in Splinter's eyes when he said 'old man' but he seemed to swallow it and kept talking.

"You have to fight against whatever is trying to take over you, or you might end up doing something you will regret for the rest of your life." Donnie looked down at the floor and then looked up again, with brown, wide eyes.

"You, don't think I'm doing this on purpose, do you?" I felt relived and took a step forward. For a moment all the signs of the Donnie we knew and loved was back in his eyes.

"Donnie?" Mikey ran up to Donnie and kneeled down in front of him. Donnie looked like a kicked puppy and I felt a small ounce of hope. But only for a few seconds. Donnie's eyes suddenly switched back to pure red and flew forward, trying to bite Mikey in the neck. Splinter reached out, grabbed Mikey's shoulder and yanked him away from Donnie's teeth. Donnie growled in anger, and stretched as far as the chains let him and tried to find someone or something to bite.

Leo and I shared a look and we both knew what was going on. What little that was left of Donnie's humanity would soon be gone, and who knew what could happen once it was gone. Leo looked at the others, who had either jumped back or (in Mikey's case) was sitting on floor and went from surprised to determined.

"Well people, lets find a way to get our brother back!"

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**A/N: Okay, it's finally up! I really hope the rest will go as smoothly, but I can't promise anything so try to be patient, okay? Please, I'm doing the best I can, and the story is harder to write than I thought and I really hope you won't stop reading this. And please again, review, favorite and follow.**


	6. Chapter 6, A monster turtle on the lose!

The monster underneath the surface

**A/N: Yay, I got this up this week! And I hope you like this chapter, because I thought over how they would try to fix the situation and the cure. Hope you like it and please, review, favorite and follow.**

Chapter 6, A monster turtle on the lose!

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(Leo's P.O.V)

This was one of the worst days I could remember. I thought Donnie had a few mood swings and some kind of wrong in his brain or something, but instead he had transformed into a big, purple, murderous monster. And then we had been forced to fight him, but didn't seem to remember who he really was. Right now he was chained to a big stone pillar, but he refused to stop fighting against the chains. He wasn't screaming at us anymore, but he was roaring in our direction, and it was really hard to see anything Donnie-like in his behavior or exterior. We were all sitting on the couch and April had Donnie's computer on her lap. She had used the bandage Donnie had wrapped around his arm to find any clues on what the heck was going on.

"Well, I'm not genius like Donnie, but from what Donnie has told me about this kind of science it looks like that purple mutagen has double-mutated his DNA and is slowly affecting his brain as well. And that part will get worse." Mikey turned to her with fear in his eyes and shook her shoulder slightly.

"What do you mean worse? How could it get worse than this?!" He gestured to Donnie who looked at us at the exact same second Mikey pointed at him, and roared at him so loudly that Mikey dove in behind Raph's back in fear. April looked at Mikey before she turned back to the computer and pressed a few keys.

"Well, you know that he can still think and talk, right? Well, that's because a small bit of 'humanity' is still left in him. But that humanity is shrinking by the minute, it won't take so long before whatever is left of our Donnie, will be gone." I took a deep breath through my nose and fought back the tears that threatened to fall. Master Splinter stepped forward and sat down beside April and placed his hand on her shoulder.

"Is there anything else you've found out? All information can be useful in this situation." April nodded, pressed a few keys again and then paled before she looked up again.

"It says here that the original mutagen in his blood is reacting with this new mutagen, and if we don't find a way to cure him in about 32 hours, he'll..." She trailed off and looked down at her feet. Raph placed his hand on her other shoulder and shook her, only a little rough.

"He'll what? April, this is really important to us, Donnie's our brother and if something bad will happen to him, we need to know!" April would usually snap at him for almost yelling at her, but know she looked up at him with big puppy eyes and almost whispered her answer.

"Well, let's just say he'll go to the big turtle terrarium in the sky if you know what I mean." Raph's eyes widened and let go of her shoulder and stared down at the floor while he shook his head in denial. Mikey gasped and covered his mouth with both hands and he shook his head too. Splinter closed his eyes, but I saw he was crestfallen. Casey just looked away and pulled his mask over his face so no one could see how he felt. I literally stopped breathing and looked over at Donnie, who didn't seem to pay any attention on us. I couldn't believe what April was saying, that Donnie could die if we didn't come up with a cure.

"No, no, no." Mikey whispered over and over and I pulled him into a hug and he started to cry into my chest. But I put on a determined face (I hope it was anyway) and turned to the rest of my family.

"Then we'll find a way to fix this! I don't care what I have to, I will do whatever it takes to save my brother!" Splinter walked up to me and placed his hand on my shoulder and looked into my eyes with a calm, but stern look in his eyes.

"Leonardo, I understand that you want to save your brother, but you must remember to be calm and patient about this. One wrong move can have devastating consequences. Use your mind, not your muscles." I nodded and turned to Raph, who also nodded with determination, and then I looked down at Mikey who also nodded into my chest.

"Can't we just use the retro-mutagen Donnie made? Won't that take away his mutation and turn him back to normal?" Casey asked and pushed the mask up again. Raph turned to him and he sounded both irritated and tired.

"Yeah, it'll take away his mutation, alright. Both of them, puckhead! What is the mutagen turns him back to a normal pet turtle again, that won't be much better, would it?" Casey blushed slightly and looked down at his knees. April tapped her finger to her chin and then smiled slightly.

"Hey, how about we go to Kurtzman for help? He knows a lot about the Kraang, the possibility is that he knows about this 'plan 37' or whatever it was called you were talking about before." She said from the couch and all of us turned to her and I realized it was a good idea. It was kind of a long shot, but it was better than nothing. I gently pushed Mikey away from my chest and dried his eyes, before I turned to both Raph and Mikey.

"Well, you heard the girl. Let's move." April was about to get up from the couch and join us, but I placed my hand on her shoulder and looked into her eyes and tried to look gentle so she wouldn't get angry.

"April, someone needs to stay with Sensei and help keep Donnie calm. Do you think you can do that? I mean, since you were good at keeping your dad calm before, when he was mutated." April at first looked like she wanted to argue, but took a breath and nodded. She took out a paper from her pocket and gave it to me.

"Donnie told me he wrote down the formula for the retro-mutagen in case he couldn't make it himself. Here is a copy he gave me a while back, in case you couldn't find it, since he has made a few things in his lab 'Mikey-proof.'" I took the piece of paper and put it in my belt.

"Thanks April. We really appreciate your help." She smiled at me and then sat back down on the couch again. Raph turned to Casey, who shook his head a little.

"Nah, I'll pass tonight. I'll stay here with April. I mean, I know it's Donnie, but he's not really in his right mind if you know what I mean." Raph nodded and we ran towards the garage and took our places in the Shellraiser.

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(Mikey's P.O.V)

The ride to Mr. Kurtzman's apartment was so quiet it was uncomfortable. I found myself looking at the empty station beside me and it felt so wrong to see the place, where Donnie was supposed to be sitting, empty. I even expected Donnie to yell at Leo to slow down or take it easier in the turns, and every time I just got disappointed. Raph seemed to notice that and turned around in his seat and looked at me and looked concerned, which was a little new.

"You okay Mikey?" I looked at him and then turned away and looked back at the map.

"What's it to you? It's not like _you_ care anyway!" I don't know why I said that, but I guess the situation had made me a little grumpier than I usually was, and I took out my anger on my brothers. Raph stood up and walked over to me and wrapped his arm around my shoulders.

"Of course I care Mikey, your my baby brother. You and Donnie mean everything to me and Leo-" I snapped my head in his direction and got even angrier, even if I had no idea where the anger came from.

"Then why do you act like you hate us?! You always pick on me and Donnie, and I can sorta understand why you pick on me, since I prank you and pester you every now and then, but what did Donnie ever do to you?!" Raph was a little taken back when I yelled him in the face, but then got angry back.

"Oh, and _you_ should talk? You pester him all the time and mess up when he's working with Kraang-things or when he's in his lab! Like when you mutated that cat into Ice Cream Kitty, or when you-!" Before Raph could finish his sentence, Leo interrupted us.

"Guys, cut it out! We're all really tired and stressed right now and you two bickering like two three year olds!" Raph sighed heavily and went back to his station with a small frown. I sighed quietly and turned to Raph, even though he couldn't see me from his station.

"Raph, I'm sorry man. I don't know why I got so angry." Raph sighed too and turned around to face me, and he looked both tired and sad at the same time.

"I'm sorry too. I guess we're all trying to deal with this situation the best we can." I nodded and turned back to my station and Raph turned back to his. A few minutes later Leo slowed down and parked the Shellraiser in an alley and we all stepped out of the car and Leo pointed to a window.

"He lives up there. Let's just hope he's home." And with that we jumped up to the fire escape and climbed up to the right window and Raph started knock on the window and didn't stop until a flash light shone us in our eyes. Mr. Kurtzman was standing a few feet away from the window, but when he saw it was us he opened the window quickly.

"Turtles? Long time no see, what brings you here?" Leo stepped forward and gave him that small dart that hit Donnie the other day and it had a teeny tiny amount of the purple mutagen left at the bottom.

"You wouldn't happen to be familiar with something the Kraang call 'Experiment 37' would you? Or the stuff in this dart?" Kurtzman took the dart and studied the purple mutagen in it and then his eyes widened a little.

"Oh, yes I know what Experiment 37 is. I've been studying it for a very long time to see if it could be stopped in any way. Have they started to put the plan in work?" Leo and Raph shared a look but before Leo could answer, he was interrupted.

"Wait a minute, where is Donatello? Shouldn't he be with you?" I bit my lip and looked down at my feet. I felt tears starting to form in my eyes and I tried to blink them away, but I felt a few tears roll down my cheeks and fell down to the floor. Leo placed his hand on my shoulder and I heard a struggle in his voice when he answered.

"That's why we're here Mr. Kurtzman. When we were investigating this Dirk Savage guy's hideout the other day, he hit Donnie with that dart and infected him with that mutagen, or what ever it is, and it turned him into a..." He trailed off and took a deep breath through his nose and then said it. "Into a monster." Kurtzman was taken back when he heard that, I could see that and he stumbled into his desk, some of the things on the desk fell over.

"Oh, my. That's very, very grave news you have. But maybe I can help, do you have a sample of his blood with you?" Raph shook his head, but took out a small usb stick with the blood test April had taken before.

"No, but we have this, April took a test on Donnie's blood before we got here, think you can use that?" Kurtzman took the stick and sat down at a computer and pressed on a few keys, looked over the results and then nodded. Leo reached down into his belt and brought the paper with the formula of the retro-mutagen.

"Donnie created a cure for the retro-mutagen, and he wrote down the formula on this paper. Maybe that can be of help too." Kurtzman skimmed through the formula, looked back to the computer and looked through the results one more time.

"Yes, I think I can use this, as well as the formula. I need to look through the results a little but more thoroughly, but if my theory is correct, then the retro-mutagen, combined with a little bit of this new mutagen, could be a solution, a cure for your brother and everyone that's been in contact with it." I felt my hope come to life again, but right after he said that my T-phone started to ring. I picked it up, saw it was April who called and answered.

"Hey April! Guess what, Mr. Kurtzman thinks he-" I was interrupted when I heard April almost screaming into the phone and immediately felt scared again. Just our typical turtle-luck working flawlessly.

"_Mikey, you guys have to get out on the roof-tops now! Donnie managed to escape and has left the lair! He's headed for the streets, you have to help us find him, NOW!_" I felt my stomach grow cold and I almost dropped the phone. If Donnie was out on the street, and someone saw him and called Dirk Savage, then we would be in big trouble.

"We'll be right there April! See ya!" I ended the call and looked at Raph and Leo, who looked both nervous and ready to act at the same time. I walked up to them and put a hand on both Raph's and Leo's shoulder and pressed my face closer to theirs to empasise what I was saying, or however it's pronounced.

"Guys we have to get out on the streets, now! There is a giant monster turtle on the lose!"

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**A/N: This one was a little easier to write, but not so easy. But I hope I can wrap this story up in maybe three or four more chapters, so it'll soon be finished. And next chapter will be a little bit of what happened back at the lair after the turtles left, and more about Experiment 37 and the cure. **

**And please, give me your opinions on which story I should write after this, new Frozen/TMNT-story or Adventure AU or a remake of my mutagen madness, since I have a few new ideas since Karai got mutated.**

**Hope you enjoyed this chapter and please, review, favorite and follow! G'night everybody!**


	7. Chapter 7, Captured

The monster underneath the surface

**A/N: Here I am with chapter 7! I'm sorry it's so short, but I tried to make this as long as possible since I am so late with this chapter, and next chapter will be up sooner I promise! I also decided to leave a few things out since I wanted to get this chapter over with so I hope you don't kill me for leaving out things I said I would have in this chapter.**

**Anyway, this chapter is finally up, so I hope you enjoy it and please review, favorite and follow! **

Chapter 7, Captured

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(April's P.O.V)

This was so messed up! No, messed up was not the right way of saying it. Donnie, who never wanted to hurt people had turned into a murderous monster and it just felt so wrong. Casey did seem sad about it but not as sad as I was, he just sat on the couch and kept an eye on Donnie with his arms crossed over his chest and looked like he was thinking 'I know you're my friend, but if you attack me or April, I _will_ hurt you.' Donnie had now stopped fighting against the chains and just sat against the pillar he was tied to and his head had fallen forward, looking really crestfallen, and I couldn't help but feel sorry for him. Monster or no monster, this was still Donnie, my best friend who had saved me so many times in the past and now he was tied up like some kind of animal, and it just didn't seem fair.

I walked up to Donnie and ignored Casey telling me to be careful and sat down a bit from Donnie, far enough so Donnie wouldn't be able to reach me if he tried, but still close enough for me to touch him. Donnie just raised his head to look at me and I saw he was both tired and sad even if it wasn't sad in a human way, more like a sad puppy way. I reached out my hand, and immediately he froze and looked at me cautiously and was on his guard like an angry guard dog and I drew back my hand slightly. But when Donnie just looked at me and made no move to attack me or bite I reached my hand towards him again and put my hand on his cheek and he relaxed a little when he saw I wasn't going to attack him pr try to hurt him. He leaned into my touch and, I might be hearing things, but I could've sworn I heard him purr ever so slightly. I moved a little closer again and put my other hand on his other cheek.

"Sh, it's okay Donnie. I know you probably don't remember me right now, but we will do everything we can to turn you back to normal." He looked at me, with no sign of understanding what I was saying, but he remained calm and I saw something familiar in his red eyes, but I couldn't see what it was. But I knew something, I was reaching him and was slowly making the Donnie I knew come back again. But of course that moment didn't last very long. Donnie decided to shift a little and raised his clawed hands towards me, and just then Casey saw what I was doing and started to yell.

"April, get away from there!" Immediately Donnie went back into monster-mode and I immediately jumped backwards just as Donnie swiped with his claw at my face. I got to my feet fast, but rather clumsy and back away from Donnie who now fought against the chains again. But this time one of the chains links snapped a little and Donnie noticed this, and with one strong pull the chain broke and Donnie's left arm was free. Casey pulled out his hockey stick, but this time he looked a little more reluctant to fight.

"Sorry, Red. I thought he was going to claw you in the face, I didn't realize he was calm." I shrugged slightly and fingered on my Tessen before deciding not to pull it out of my pocket.

"It's okay Jones. Just next time, try to look before you yell 'wolf', okay?" Donnie had started to bite on the chain that held his right arm and managed to bite through the metal enough so he could, with another strong pull, break the chain and he was free. By this time, Master Splinter had come out of the dojo and saw that Donnie was free and stepped up to me and Casey.

"Donatello, my son. Calm yourself. Remember who you are, my son." Donnie just roared in response and ran forward to attack Splinter, who easily dodged the attack, but he didn't count with Donnie's new tail, and it managed to hit Splinter right over his eyes. Master Splinter stumbled back a little and covered his eyes, and this gave Donnie a slight advantage and he kicked Splinter in the knees, making him fall to the ground.

Casey ran forward and raised his hockey stick to hit Donnie in the stomach, but Donnie just swiped at him like you swipe at a fly and Casey flew into the wall with a loud crack when he hit his back into the wall. When Donnie turned to me I just raised my hands and walked up to him, calmly and reassuringly.

"Donnie, calm down. It's okay, calm down." Donnie still growled and snarled at me, but he didn't attack, he just stood there and watched me. Master Splinter had regained his sight again, but chose to see how things went before he should attack. He walked up to Donnie and reached out his hand slowly.

"Donatello, it's alright. You are with your friends and with me. We'll help you, just calm down. Remember who you are, my son." He was close to Donnie, but not so close so he could bite me. He leaned towards Master Splinter's face and smelled him like a dog would smell you, and then pulled away from Splinter and I saw something familiar in his eyes again.

"Fa-ather-r?" It sounded like something between a growl and a snarl but that one word was understandable enough to us to know what he said. Master Splinter's eyes widened slightly at Donnie's word, but before anyone could say or do anything, Donnie ran for the exit, jumped over the turnstiles and ran into the sewers. Casey had gotten to his feet by now and both he and I looked to Master Splinter for orders. He looked at us, then grabbed his staff which he had dropped on the floor when Donnie attacked him.

"We need to go after him! April, call his brothers, tell them to look for him as well!" I nodded and while we started to run after Donnie I called up Mikey and told him quickly about the situation. Mikey said they would be out there and look for Donnie, so I hoped they would find him quickly or someone else might do.

* * *

(Raph's P.O.V)

"You would think that a big, purple mutant turtle would be easy to find, but oh no! It's hard enough as it is to find a cure for him, why does he have to complicate things for us?" I know I shouldn't be angry at Donnie, but I couldn't help it. When April told us Donnie had escaped the first reaction I had was 'are you kidding me?' but now I got more and more worried. What if Dirk Savage found him? What would he do to Donnie then? Leo turned to me and shrugged slightly.

"We have to keep looking! If Dirk Savage finds him and captures him, we'll have to hurry even more to both get him back and cure him, so shut up and keep looking!" Normally I would yell at him for telling me to shut up, but I decided to swallow it this one time. We had more important things to do now! Mikey stopped and looked down into an alley and pointed at a container.

"Leo! Raph! I see him, behind that container!" Leo and I ran up beside Mikey and looked down and immediately saw Donnie moving out from behind the container and into the light of the city lights. It felt so strange to look at this creature and say to yourself that it's your brother in that body.

"Donnie..." Mikey sounded like he wanted to cry, and I could understand why. This was the first time we saw him in the light and he really looked scary, but at the same time I saw some small details that was similar with the Donnie I knew.

"Let's go down there, knock him out and bring him back to the lair. Mikey, call April again and tell her and the others to come here!" Mikey nodded and pressed a few buttons on his phone, while Leo and I jumped down to the street and reluctantly draw our weapons. But before we could start fighting him, a big black van drove up to the alley and a familiar face showed himself. Dirk Savage stepped out the van.

"Hello again, turtles. Thank you for leading me the perfect mutant. Now, hand him and your-selves over to me, and nobody gets hurt." I pulled out my Sai, grateful to fight someone else but my brother. Leo drew his swords and stepped in front of Donnie to protect him.

But Donnie didn't seem to want to be protected and threw Leo to the side and ran forward to attack Dirk himself, but Dirk just pulled out a small gun and shot Donnie with a dart that hit him in the shoulder. But Donnie didn't seem affected by the dart and swiped his tail at Dirk's head and landed a hit at his temples. But Dirk grabbed his tail and yanked Donnie back to him and grabbed his gun and hit Donnie as hard as he could on the side of his head. I felt my anger boil over and I couldn't help it.

"Okay, that's it! You're going down Savage!" I ran headlong into the battle with raised sai's and tried to stab him in the head, but remembered he was a human and not a robot a little too late and that gave him the advantage and he grabbed my arm and threw me into the wall, but I recovered quickly and managed to cut through his gun and then landed a kick in his ribs. Mikey jumped down but didn't charge into the battle as well, he tried to protect Donnie, while I backed him away from both him and Donnie, who lay unconscious on the ground.

Leo had drawn his swords now and helped me with Savage, and it worked pretty good. Dirk was strong, but not strong or skilled enough to keep an eye on both of us. Leo managed to sweep him off his legs and put the tip of his sword to Savage's throat to keep him down. But that didn't stop Savage for very long. He drew out a small grenade, and before anyone could figure out what happened he threw it to the ground and a big cloud of smoke filled the alley and the next thing I knew I fell to the ground and the world turned black.

"_Raph? Raph, wake up man!" _I groaned as I felt someone shake me, and a familiar, yet annoying voice tried to wake me. I waved my hand in the direction the voice came from and pushed away the person who tried to wake me up.

"Aw, come on Raph! Wake up already!" I felt a slap across my face and I flew up from the ground, and my head slammed against Casey's and both of us yelped in pain and surprise and my hand flew up to my forehead to run away the pain. I looked around and saw April waking up Mikey and Splinter waking up Leo. But I saw no trace of Donnie anywhere.

"Are you guys okay? We came here as soon as we could and when we arrived we saw you guys out cold and Donnie was gone! What happened?" April sounded frantic, and I could understand why, but now I was worried about Donnie and angry at Dirk Savage. Leo sat up and rubbed his head.

"We tried to fight off Dirk Savage before he could get his hands on Donnie, but he knocked us out before we could get out of here. And now he has Donnie, and who knows what he'll do to him." April gasped in fear and covered her mouth while shaking her head in denial. Casey's eyes widened in fear and dropped his hockey stick. Master Splinter closed his eyes and took a deep breath, and I could see he was trying to hold back his emotions.

"And what about that cure? Have you found a cure?" Leo nodded and told Splinter about Kurtzman's theory about that cure and that he was testing it right now. April stepped forward and placed her hand on Leo's shoulder.

"Master Splinter and I can go back to Kurtzman and watch over how things go with the cure. You guys can go and try to get Donnie out of Savage's hideout. Sounds like a plan?" Leo nodded and turned to me, Casey and Mikey.

"Okay guys. Let's go and get Donnie out of there!" And with that April and Splinter left the alley and ran towards Kurtzman's apartment, and the rest of us ran towards that old warehouse to get our brother back.

* * *

**A/N: Okay I am not very happy with how this chapter turned out, but I just wanted to get this done, so I hope you can take it and keep on reading this story, cause I know this chapter is not my best. Please, cut me some slack if you don't like this. And please review, favorite and follow. **


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